1. Field of the Invention
The present invention relates to a head slider suitable for a magnetic disk device (hard disk drive) of a computer or the like, and to a magnetic disk device including the same.
2. Description of the Related Art
A magnetic disk device comprises a head slider. For example, as shown in FIG. 1, when information is written on or read out from a magnetic disk 5 of a magnetic disk device 100, the head slider 1 is positioned against the magnetic disk 5. Then, as for example shown in FIG. 2, it floats over the magnetic disk 5 due to an air current produced on the surface of the rotating magnetic disk 5. At this time, if the flotation amount of the head slider 1, i.e., the gap between the head slider 1 and magnetic disk 5, is too large, recording can no longer be performed. Therefore, in the head slider 1 of the prior art, as shown for example in FIG. 3, a negative pressure part 10 which generates a negative pressure aspirating it towards the magnetic disk 5 on the surface (ABS: Air Bearing Surface) facing the magnetic disk 5, is provided which balances the flotation by the negative pressure so that the flotation of the head slider 1 is controlled to a fixed amount.
However, the flotation amount of the head slider, i.e. the gap between the head slider and rotating magnetic disk, is on the order of just several nanometers. For example, considering that the diameter of a virus is of the order of 200 nm, it can be appreciated how small this number is. In order to realize stable recording with the magnetic disk device, an interval of several tens of nanometers from the rotating magnetic disk must be maintained when the head slider is in use. Consequently, the design of the head slider is extremely difficult.
The design of the head slider requires the following:
(1) the head slider must be able to maintain a uniform flotation amount from the inner area to the outer area of the magnetic disk (as the speed of the outer area of the magnetic disk is approximately twice as much as that of the inner area and the speed vector direction varies by approximately 25°, it must be able to maintain a uniform flotation amount taking this point into consideration),
(2) the head slider must be able to maintain a fixed flotation amount during a seek operation (as the flow velocity direction varies by approximately 15°, it must be able to maintain a fixed flotation gap taking this point into consideration),
(3) it must be possible to use the head slider even when the atmospheric pressure varies (ensuring that it can be used at an altitude of 3000 m), and
(4) it must be possible to use the head slider even when there are manufacturing errors or assembly errors (considering that the gap between the head slider and magnetic disk is only of the order of several tens of nanometers, manufacturing or assembly errors are serious defects which are not normally allowed, but it must be possible to use the head slider even in these circumstances).
In recent years, with increasing recording densities of magnetic disks, a demand has emerged to reduce the flotation amount of the head slider even further. However, if the flotation amount is further reduced, when the slider is used at high altitude, the flotation amount decreases still further due to the drop in atmospheric pressure, and the head slider and magnetic disk may come in contact which damages the magnetic disk so that recording can no longer be performed, which is a serious problem. Therefore, of the aforesaid requirements (1)–(4) in designing the head slider, (3), i.e., the ability to use the head slider even when there is an atmospheric pressure change (ensuring that it can be used at an altitude of 3000 m) is a key point.
In the prior art, to resolve this problem, it has been proposed for example in Japanese Patent Application Laid-Open (JP-A) No. 2000-57724 to adopt a design wherein, in the aforesaid head slider, the ratio (deep groove depth R/shallow groove depth δs) between the “deep groove depth R” and “shallow groove depth δs” is larger than 5. However, in this case, as the range in which the variation of flotation amount is small relative to groove depth variation is actually very narrow, the groove depth is limited and it is difficult to set the groove depth to the optimum value relative to the scatter in the manufacturing procedure. It has also been proposed to provide a standard atmospheric pressure pocket inside the head slider and perform pressure control of this standard pressure pocket, so that the reduction of flotation amount due to pressure drop is suppressed. However, in this case, as it is necessary to provide the standard atmospheric pressure pocket, the construction becomes more complicated and manufacturing costs increase.
Therefore, a head slider which maintains a uniform flotation amount from the inner area to the outer area of a magnetic disk, maintains a fixed flotation gap even during seek operations, has no limitation of groove depth wherein the fluctuation of flotation amount relative to groove depth can be optimized, does not require additional structures or manufacturing costs, is not subject to limitations due to manufacturing errors and assembly errors and which can be used even if the atmospheric pressure varies (can be used even at an altitude of 3000 m), and a high-performance magnetic disk device comprising the same, had still not been proposed.
It is therefore an object of the present invention, which was conceived to resolve the aforesaid problems inherent in the prior art, to provide a head slider which maintains a uniform flotation amount from the inner area to the outer area of a magnetic disk, maintains a fixed flotation gap even during seek operations, has no limitation of groove depth wherein the fluctuation of flotation amount relative to groove depth can be optimized, does not require additional structures or manufacturing costs, is not subject to limitations due to manufacturing errors and assembly errors and which can be used even if the atmospheric pressure varies (can be used even at an altitude of 3000 m), and a high-performance magnetic disk device comprising the same.